The present invention relates to a sound absorbing device to be mounted on a sound insulation wall which is installed, for instance, by the side of an expressway to insulate noise caused by passage of vehicles.
For example, Japanese Patent Application Examined Publication No. Sho. 51-46969 and Japanese Utility Model Application Unexamined Publication No. Sho. 62-186200 disclose mounting a sound absorbing device on top of a sound insulation wall which is installed, for instance, by the side of an expressway. However, these conventional sound absorbing devices have the following disadvantages. First, to fix a long cylindrical sound absorbing device having a relatively large diameter to the top of an upright sound insulation wall, tightening bands for the sound absorbing device and metal fixing parts therefor need to be separately provided on top of the sound insulation wall. To prevent drop of the sound absorbing device, wires need to be used so as to penetrate through the sound absorbing device in its radial direction and to be fixed to the wall. Further, the size of the fixing metal parts for the sound absorbing device needs to be adjusted for that of the sound insulation wall. Therefore, a complicated work is needed to install the sound absorbing device with the use of a large number of parts.
Further, the appearance is very poor because the cylindrical sound absorbing device is provided on top of the upright sound insulation wall, the former is fixed to the latter with the bands at intervals of several meters, and the band fixing parts protrude sideways.
An additional work of filling the space between the flat top surface of the upright sound insulation wall and the cylindrical sound absorbing device makes the fixing operation unduly longer.